The current public interest in pollution control has created the need for surveilance and monitoring of environmental conditions particularly related to plant effluent, waterways, sewers, lakes and rivers. The acquisition of accurate and reliable data regarding water quality as affected by industrial wastes, treatment plant effluent, meterological and other factors is necessary for effecting enforcement of standards for pollution control, as well as for analysis and planning.
Automated water quality monitoring systems include monitors at field stations connected by telemetry to a central control data receiving station and rely on the use of automatic unattended measurement procedures operated on a continuous basis, or intermittently, at a predetermined frequency. Sophisticated instrumentation for automatically analyzing physical and chemical parameters, such as pH, conductivity, temperature, dissolved oxygen, chlorides and turbidity of plant effluent and waterways have been utilized in the art. It is recognized that instrument reliability is adversely affected by the fouling of the sampling system or malfunction of the analyzer components that are continously exposed to polluted water. Heavy build-up of slime, algae or particulate matter on the sensing probes, which may comprise solid state or liquid membrane electrodes, and on the surface areas confining the water surrounding the probes, with resulting stagnation of flow deleteriously affects the sensitivity of the probes resulting in inaccurate measurements or measurement failure.
In order to obtain reliable data it has been found necessary to clean the sensing probes manually at frequent periodic intervals, preferably, at least daily. Monitoring stations which are remotely located at substantial distances from a central receiving station must be visited daily by service personnel to effect manual cleaning of the probes and associated apparatus. This requires extensive travel, as well as a substantial expenditure of labor by the service personnel, and represents a significant cost in the maintenance of monitoring stations in the system under consideration. It also has been found that manual removal or displacement of the sensing probes from the monitoring apparatus for manual cleaning disturbs the stability of the calibration resulting in unreliable data.